Impetigo: Symptoms, Types, Causes and Treatment

Impetigo is a common skin infection that primarily targets children but can also affect adults. Highly contagious yet usually mild, this bacterial infection is known for its characteristic lesions and rapid spread, especially in close-contact settings. Understanding the symptoms, types, causes, and modern treatment options for impetigo is essential for timely diagnosis, effective management, and prevention of complications. This article provides a comprehensive, evidence-based overview of impetigo, synthesizing the latest clinical research and guidelines.

Symptoms of Impetigo

Impetigo presents with distinctive skin changes that can be alarming for patients and caregivers. Recognizing its signs early is crucial for preventing transmission and complications. While the infection often starts as minor skin irritation, it can progress rapidly, especially in children.

Symptom	Appearance	Common Sites	Source(s)
Sores/Lesions	Red spots, quickly rupturing	Face, arms, legs	1 4 8
Honey-colored Crusts	Golden-yellow, sticky crusts	Mouth, nose, extremities	1 4 8
Blisters/Bullae	Large, fluid-filled blisters	Trunk, folds	1 2 4
Itching	Mild to severe itching	Lesion sites	1 8

Table 1: Key Symptoms

Classic Signs and Lesion Progression

Impetigo typically begins as small red spots or papules, which rapidly become fluid-filled vesicles or blisters. These blisters quickly rupture, releasing pus and forming thick, honey-colored (golden-yellow) crusts—a hallmark of impetigo contagiosa (nonbullous impetigo) 1 4 8. The crusts are sticky and may be surrounded by redness.

Distribution and Sites Affected

• The face (especially around the nose and mouth) is most commonly affected.
• Lesions may also appear on the arms, legs, and other exposed skin.
• In bullous impetigo, blisters tend to form on the trunk and in skin folds (intertriginous areas) 1 4.

Associated Symptoms

• Itching is frequent and can be intense, leading to scratching and secondary spread.
• Pain is usually minimal, but mild tenderness can occur.
• Systemic symptoms (fever, malaise) are rare and typically only seen in severe cases or complications 1 4 8.

Complications to Watch For

Although rare, complications such as post-streptococcal glomerulonephritis (a kidney inflammation) can occur, particularly with infections caused by Streptococcus pyogenes 1 3 5. Cellulitis and deeper infections are uncommon but possible if lesions are left untreated.

Types of Impetigo

Impetigo is not a single entity but rather a group of related skin infections. Each type has unique features, though overlap is common, and more than one type may be present in the same patient.

Type	Distinctive Feature	Primary Pathogen	Source(s)
Nonbullous	Honey-colored crusts	S. aureus, S. pyogenes	1 2 4 8
Bullous	Large, flaccid blisters	S. aureus	1 2 4 8
Mixed/Other	Overlapping features	Both organisms	2 7

Table 2: Types of Impetigo

Nonbullous Impetigo (Impetigo Contagiosa)

• Prevalence: Most common form, accounting for approximately 70% of cases 1.
• Lesions: Begin as papules or vesicles, quickly rupturing to form the characteristic golden-yellow crusts.
• Pathogens: Caused by either Staphylococcus aureus, Streptococcus pyogenes, or both 1 2 4 8.
• Location: Primarily on the face and extremities.

Bullous Impetigo

• Prevalence: Accounts for about 30% of cases, more common in infants and young children 1 2 4 8.
• Lesions: Large, fluid-filled blisters (bullae) that are fragile and rupture easily, leaving a thin, brownish crust.
• Pathogen: Caused exclusively by Staphylococcus aureus 1 2 8.
• Location: Favors the trunk and intertriginous (skin fold) areas.

Mixed or Overlapping Forms

• Some patients exhibit features of both types, with varying lesion appearances coexisting 2 7.
• Mixed infections with both S. aureus and S. pyogenes are not uncommon 7.

Causes of Impetigo

Understanding what causes impetigo helps in both prevention and targeted treatment. The infection is primarily bacterial, but several risk factors and transmission routes play key roles in its spread.

Cause/Factor	Description	Risk Population	Source(s)
S. aureus	Main pathogen for all types	Children, adults	1 2 7 8
S. pyogenes	Especially in nonbullous	Young children	1 2 5 8
Skin Trauma	Entry via cuts, bites	Atopic dermatitis	1 8
Close Contact	Spread in schools, families	Children	4 7 8

Table 3: Causes and Risk Factors

Key Bacterial Agents

• Staphylococcus aureus: The most common cause, responsible for all bullous impetigo and the majority of nonbullous cases. Methicillin-resistant strains (MRSA) are increasingly important, influencing antibiotic choices 1 8 9.
• Streptococcus pyogenes (Group A Streptococcus): Especially important in nonbullous impetigo and in post-infectious complications like glomerulonephritis 1 2 5 6 8.

How the Infection Starts

• Skin Barrier Disruption: Impetigo often occurs at sites of minor trauma, such as scrapes, insect bites, eczema, or other pre-existing skin conditions 1 8.
• Colonization: S. aureus often colonizes the nasal passages first, then spreads to the skin; GABHS binds directly to exposed skin proteins 8.
• Secondary Infection: Impetigo may infect pre-existing lesions, including atopic dermatitis and herpetic lesions 1 6 8.

Transmission and Risk Factors

• Direct Contact: Impetigo spreads rapidly via skin-to-skin contact, making outbreaks common in child care settings, schools, and families 4 7 8.
• Fomites: Sharing towels, clothing, or bedding can facilitate spread.
• Climate: More common in warm, humid environments 3.

Complications and Systemic Effects

• Glomerulonephritis: Especially linked to streptococcal impetigo; certain bacterial strains are more nephritogenic 3 5.
• Immunomodulation: S. pyogenes infections can modulate immune responses, particularly in patients with atopic dermatitis 6.

Treatment of Impetigo

Prompt, effective treatment of impetigo relieves discomfort, shortens disease duration, and limits transmission. Both topical and oral antibiotics are used, and new therapies are emerging. Antibiotic resistance is a growing concern and influences therapeutic choices.

Therapy Type	Example	Indication	Source(s)
Topical Antibiotic	Mupirocin, fusidic acid, ozenoxacin	Localized disease	1 4 10 11 12
Oral Antibiotic	Cephalexin, amox/clav, clindamycin	Extensive/multiple lesions, MRSA	1 4 8 10
Natural Remedies	Tea tree oil, Manuka honey	Anecdotal, not evidence-based	1
Disinfectants	Antiseptic washes	Not recommended	1 4 10

Table 4: Main Treatments for Impetigo

Topical Antibiotics

• First-line for Localized Disease: Mupirocin and fusidic acid are highly effective, with cure rates exceeding 90% in mild cases 1 10 11.
• Ozenoxacin: A newer topical agent, shown to be effective and well-tolerated in clinical trials for both adults and children 12.
• Duration: Typically applied for 5–7 days 10 11 12.
• Superiority: Topical antibiotics are generally superior to placebo and at least as effective as oral antibiotics for localized disease, with fewer side effects 10 11.

Oral Antibiotics

• Indications: Reserved for patients with extensive disease, large bullae, deep tissue involvement, or when topical therapy is impractical 1 4 8.
• Options: Include cephalexin, amoxicillin/clavulanate, clindamycin (for MRSA), and others. Penicillin is not recommended due to poor efficacy 1 4 10.
• Resistance Considerations: Local resistance patterns (e.g., MRSA, fusidic acid-resistant S. aureus) must guide antibiotic choice 1 9 10.

Natural and Adjunctive Therapies

• Home Remedies: Products like tea tree oil, olive oil, and Manuka honey are anecdotally reported to help but lack robust clinical evidence 1.
• Disinfectants: Not recommended, as they are less effective than antibiotics and do not improve cure rates 1 4 10.

Emerging Therapies

• Minocycline Foam: Under development for resistant cases 1.
• Ozenoxacin: Recently approved and offers a new option for topical therapy 12.

Managing Antibiotic Resistance

• Surveillance of local resistance trends is important, particularly with the rise of MRSA and fusidic acid-resistant strains 1 9 10.
• Restrictive use of topical antibiotics like fusidic acid is advised to slow resistance development 9.

General Management Tips

• Hygiene: Keeping lesions clean, avoiding scratching, and not sharing personal items can help prevent spread 4 8.
• Isolation: Children with impetigo should stay home from school or daycare until 24 hours after starting effective therapy 4.
• Follow-up: Most cases resolve within 1–3 weeks, with or without scarring 1 4.

Conclusion

Impetigo is a common, highly contagious skin infection—especially in young children—that can be recognized by its characteristic honey-colored crusts (nonbullous type) or large, fragile blisters (bullous type). Most cases are caused by Staphylococcus aureus and/or Streptococcus pyogenes, often entering through minor skin trauma. Effective treatment relieves symptoms, shortens illness duration, and limits spread, with topical antibiotics being the mainstay for localized disease. Oral antibiotics are reserved for more severe or widespread cases. Ongoing surveillance for antibiotic resistance and strict hygiene practices are essential for effective management and prevention.

Key Takeaways:

• Impetigo is most common in children and spreads rapidly through close contact and minor skin injuries.
• Two main types exist: nonbullous (honey-colored crusts) and bullous (large blisters).
• The main causative bacteria are S. aureus and S. pyogenes.
• Topical antibiotics (mupirocin, fusidic acid, ozenoxacin) are first-line for localized disease; oral antibiotics are for extensive or resistant cases.
• Disinfectants and most natural remedies lack evidence and are not recommended.
• Growing antibiotic resistance requires careful antibiotic selection and prudent use.
• Good hygiene and prompt treatment are vital for controlling outbreaks and preventing complications.